The present invention relates generally to optical communication systems and more particularly, to micro-electro-mechanical optical devices.
Optical communication systems typically include a variety of optical devices (e.g., light sources, photodetectors, switches, attenuators, mirrors, amplifiers, and filters). The optical devices transmit, modify, or detect optical signals in the optical communications systems. Some optical devices are coupled to micro-electro-mechanical structures (e.g., thermal actuators) forming a micro-electro-mechanical optical device. The term micro-electro-mechanical structure as used in this disclosure refers to a microscopic structure that moves mechanically under the control of an electrical signal.
Cowan, William D., et al., xe2x80x9cVertical Thermal Actuators for Micro-Opto-Electro-Mechanical Systemsxe2x80x9d, SPIE, Vol. 3226, pp. 137-146 (1997), describes a micro-electro-mechanical structure useful for moving optical devices. In Cowan et al., the micro-electro-mechanical structure is a thermal actuator. The thermal actuator is coupled to an optical mirror. Both the thermal actuator and the optical mirror are disposed on a surface of a substrate. The thermal actuator has multiple beams. A first end of each beam is coupled to the optical mirror. A second end of each beam is attached to the substrate surface.
Each beam of the thermal actuator has two material layers stacked one upon the other. The stacked material layers each have a different coefficient of thermal expansion.
The thermal actuator mechanically moves the optical mirror in response to a current being applied to the beams. Applying the current to the beams heats the stacked material layers. As the beams are heated, at least a portion of each beam is heated above the brittle to ductile transition of the material layers, causing a permanent mechanical deformation thereto which remains upon cooling. When the beams deform a first end of each beam as well as the optical mirror coupled thereto lift a predetermined height above the plane of the substrate surface. Such micro-electro-mechanical structures provide a limited range of motion for optical devices coupled thereto which makes them undesirable.
Therefore, micro-electro-mechanical optical devices capable of controlling the movement of the optical devices coupled thereto continue to be sought.
The present invention is directed to a micro-electro-mechanical optical device. The micro-electro-mechanical optical device includes a micro-electro-mechanical structure coupled with an optical device. Both the micro-electro-mechanical structure and the optical device are disposed on a substrate surface. The micro-electro-mechanical structure lifts the optical device a predetermined distance above the plane of the substrate surface. Thereafter, the lifted optical device is moveable relative to the plane of the substrate surface in response to an electrostatic field generated between the optical device and the substrate.
The micro-electro-mechanical structure includes a plurality of first and second beams. A first end of the plurality of first beams is coupled to a plate in hinged attachment with the substrate surface. The hinged plate includes a v-shaped notch. The hinged plate is coupled to an engagement plate. A first end of the plurality of second beams is coupled with the engagement plate. The engagement plate is also coupled with the optical device. When unassembled the beams, the hinged plate, and the engagement plate lie flat on the substrate surface.
The engagement plate has a pair of v-shaped notches located at opposite ends thereof. Each pair of v-shaped notches on the engagement plate is located within the region of the v-shaped notch on the hinged plate.
First ends of the plurality of first beams lift in an upward direction, substantially in an arc, above the plane of the substrate surface in response to the application of an activation force. As the first ends of the plurality of first beams are lifted above the plane of the substrate surface, they rotate the hinged plates out of the plane of the substrate surface. When the hinged plates are rotated out of the plane of the substrate surface, the plurality of second beams lift the engagement plate as well as the optical device above the plane of the substrate. As the engagement plate is lifted, it completes the rotation of the hinged plate started by the first beams so that the hinged plates are about ninety degrees out of the plane of the substrate.
A variety of activation forces can be applied to the beams to lift the optical device. Suitable examples include thermal contraction of the beam layers, beam contraction due to intrinsic stress, and electromagnetic forces.
After the optical device is lifted above the plane of the substrate surface, an electrostatic field is generated between the lifted optical device and the substrate surface. The electrostatic field is generated by applying a bias voltage between the optical device and a portion of the substrate. The electrostatic field moves the optical device by deflecting (or rotating) the optical device toward the substrate surface. The deflection distance of the optical device depends on the amount of the applied bias voltage.
Both the substrate and the optical device are preferably conductive so that the bias voltage may be applied thereto. When either of the substrate or the optical device are insufficiently conductive to deflect such optical device toward the substrate surface, conductive layers (e.g., electrodes) are optionally formed on regions thereof.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and do not serve to limit the invention, for which reference should be made to the appended claims.